[amsat-bb] Re: Dumb question 9600 FSK

On Thu, Nov 21, 2013 at 03:45:04PM -0700, David W0DHB wrote:

What mode should your RX be in to receive the 9600 baud FSK telemetry downlink signals. USB, FM ??

It should be FM, and you must pick up the signal from before the audio filter. You're looking for "flat unsquelched" in Motorola parlance ;-)

9600bps FSK is generated by modulating the carrier frequency with the digital bitstream directly, after passing it through a filter to round the corners off so it doesn't splatter. As such, the frequency response needs to be flat from DC to whatever the passband of the IF filter is.